"The use of patents as references is not limited to what the patentees describe as their own inventions or to the problems with which they are concerned. They are part of the literature of the art, relevant for all they contain." In re Heck, 699 F.2d 1331, 1332-33 (Fed. Cir. 1983) (quoting In re Lemelson, 397 F.2d 1006, 1009 (CCPA 1968).

In addition, we emphasize that, although secondary considerations such as unexpected results must be taken into account, they do not necessarily control the obviousness conclusion. Intercontinental Great Brands (Kraft) v. Kellogg, 869 F.3d 1336, 1345--46 (Fed. Cir. 2017) (there are some prima facie obviousness cases so strong that they are impossible to overcome even with the best possible secondary indicia of nonobviousness)